Problem: $\dfrac{9}{3} - \dfrac{8}{12} = {?}$
Solution: $ = {\dfrac{9 \times 4}{3 \times 4}} - {\dfrac{8 \times 1}{12 \times 1}} $ $ = {\dfrac{36}{12}} - {\dfrac{8}{12}} $ $ = \dfrac{{36} - {8}}{12} $ $ = \dfrac{28}{12}$